As highlighted at Brave New Climate a few months ago, there are journalists who opt to report on matters of radiological hazard without providing context, or necessarily understanding what they are saying. I was glad to recently see an article on tsunami risk that resisted mentioning nuclear catastrophe, but the fact remains that the overall public ambivalence to precise measurements and estimations, and what they tell us about absolute and relative hazards, is largely unchalleneged, and often exploited.
Except it’s really not that hard, I promise! Most people can imagine a lump of stuff sitting there, radiating alphas, betas and/or gammas. Which of these predominates, and how hazardous their energy is depends on the isotope and its total mass, which is referred to in becquerels – just think of it like the weight, but specifically for a given radioisotope.
The normal smoke alarms in your house contain 37 000 becquerels each of americium-241. I know there are non-ionising models, I used to sell them occasionally in a previous life (often to customers who loudly proclaimed they were safer). Am-241 has a half-life of 432 years, and releases mostly alpha particles. You can read more here, but the point is we don’t have to imagine stuff any more, we can think of a smoke alarm. Ever wondered what’s inside one? I did. I also have a personal dosimeter, so it’s experiment time.
Micro Sieverts per hour (μSv/h) are what we’re all receiving constantly as an average dose of radiation. Despite my grasp of the metrics, principles and cellular biochemistry involved, I’m not an expert, but 0.1 μSv/h? I wouldn’t worry.
Controversy! Ubiquitous household item blasts five times the normal radiation at your family every hour! Well, of course such a sensationalised yet technically true statement seems like hyperbole now. Still, I admit that I’d forgotten I’d set the threshold at 0.3 and when the alarm screamed, I jumped! The round yellow shroud in the top photo can be convinced away from the circuit board, and-
After a minute it settled at around 1.8 μSv/h. Spectacular! If you remember the figures from Geoff’s article, Catalyst was worried about 7 μSv/h in Fukushima prefecture, but they didn’t provide context. Is this context? This is a ubiquitous domestic safety device which dramatically reduces the chance of death in the event of a house fire. Apart from the odd customer, everyone’s used to them. Could they be causing cancer anyway? I don’t think so at all, and here’s why.
I trust everyone’s heard of the Radium Girls. Apparently, not a few of the workplace protections we take for granted originated with their fight for a bit of justice. Initially, they were provided with no guidance regarding the safety of pointing the brushes for dial painting with their lips, and ingesting concentrated radium-226 and radium-228 in the process. The bioaccumulation above a threshold resulted in serious health impacts. 100 “microcuries” equals 3.7 million becquerels – a couple orders of magnitude higher than in my smoke alarm, which I managed not to swallow. The study showed that the significant population of workers who absorbed a dose below this threshold avoided the horrendous bone malignancies characteristic of radium exposure. This was achieved through safer work guidelines, not by removing the isotopes. The proportionally fractional amount of Am-241 is even safer as a labelled, discrete button in its tight housing – a form that cannot realistically enter a human body, especially while properly encased and screwed to your hallway ceiling.
But no one’s worried about radium – or americium – at Fukushima! It’s the cesium, right? Well, whichever isotope has little relevance at low exposures,* but the substantial exposures from unsecured medical supply of cesium-137 at the centre of the 1987 Goiânia accident led to five deaths. How many becquerels? 7 000 000 000 000 were thought to have been spread throughout the environment, from an initial 50.9 trillion. A substantial population – who pointedly didn’t die of radiation syndrome or cancer – received doses many orders of magnitude larger than what my eviscerated smoke alarm could emit, and, indeed, than one can conceivably absorb by eating the feared matsutake mushrooms of Minamisoma City. 102 900 becquerels per kilogram! shrieked one hysterical website just last week. Would I eat them? Not a whole kilogram, just like I wouldn’t drink the seawater downhill from the Fukushima Daiichi plant, tritium or no tritium. Of course no one should be expected to eat contaminated fungus, but no one should be perpetuating context-free agitation about how dangerous it is either, when we have history as such a stark guide.
And particles from reactors? People hunt them.
It is quite clear that there is a threshold below which radiation, isotopes and decays do no harm. What might that threshold be, though? There’s much healthy discussion, but one source recently stated:
For all of the above reasons, it is recommended that use of the linear no-threshold (LNT) model be abandoned and replaced by a more realistic approach to the estimation of radiological risks. A new model to replace LNT should be based on thresholds below which risks are considered to be zero. In accordance with present knowledge and data, thresholds are considered to be within the following ranges depending on circumstances. These figures are proposed as a basis for further discussion:
– Within the range 50-300 mSv for acute single doses to adults;
– Within the range 100-700 mSv per year for continuous chronic exposures; and
– Within the range 50-200 Bq/m3 for naturally occurring radon in the air breathed in confined spaces, which causes about half the exposure to background radiation for many people.
Thresholds also need to be developed for the sum totals per year, per month or per week of intermittent and protracted exposures, and for acute single doses to embryos, foetuses and infants.
Risks might be assumed to depend on, or be proportional to, the incremental dose or dose rate over limited ranges above the relevant threshold. Simple explanations of the meaning and level of actual risk and benefits should be developed.
That 700 mSv/yr equates to just shy of 80 μSv/h. Even the lower end of that range is 11.4 μSv/h – granting considerable breathing room for any visitors to Fukushima. So what is the opposition actually afraid of? Do they have better empirical information than such experts? What might it be, and how might it account for the few examples I’ve provided, and the numerous others that exist, of the benignity of low dose radiation? And, importantly, how is it of sufficient gravity to justify existing stringent limitations than have caused far more harm than benefit? No, seriously – if I’ve erred here, I want to know. I’ll remove this article if the evidence shows it’s wrong. But as things stand, a triple reactor disaster three and a half years ago has resulted in contamination that will not harm the population that it continues to terrify. If there’s no evidence forthcoming, then those vocal nuclear critics have a whole lot of explaining to do.
To their credit, we do have journalists who approach these matters with very open minds when honestly exploring the potential for nuclear energy in Australia, new technology or the prospects of an interim waste facility. To my mind the crucial axis this all hinges on is the willingness of people to hear what our experts have to say, and to approach the opposing messages of fear and indolent bias with razor-sharp skepticism.
*Except possibly for special cases like iodine-131 that essentially attacks the thyroid unless the dose is medically controlled, one isotope is as effectively harmless as another, contamination-wise, at such low exposures. Why? Look at that radium study again:
Ra-226, half-life 1620 years, emits an alpha particle, and is transformed into radon (half-life 3.8 days); eight more radioactive decays, which emit either alpha or beta particles, take place before it becomes an atom of non-radioactive lead.
All of those workers who didn’t develop symptoms had all these various mixed-up isotopic decays occurring in their bodies, of different energies and in different organs. It’s hard to be more precise about it, but it happened.